The present invention is generally related to radiotelephones, and more particularly to a cellular telephone with a standard telephone set.
Cellular telephones currently are operated with a special purpose handset that is coupled via audio and data buses to a cellular telephone transceiver. In order to avoid use of a cellular radio channel during dialing and minimize costs of cellular telephone calls, cellular telephone users are required to dial a telephone number and then press a "SEND" button (pre-origination dialing), in order to place a cellular telephone call. Pressing the "SEND" button causes the cellular telephone handset to generate a "SEND" signal and append it to the dialed digits transmitted to the cellular telephone transceiver.
When a conventional pulse or tone dial telephone set or equivalent machine, such as a modem, is used in association with a cellular telephone, there is a need for either a "SEND" button or circuitry that simulates the "SEND" function. A "SEND" button can be added to a conventional telephone set by using a # or * button or hookswitch flash, both requiring additional circuitry and/or software in an interface device.
A "SEND" button can also be simulated by detecting the end of dialing and automatically generating the "SEND" signal in the same manner as is done by the cellular telephone handset. Detecting the end of dialing and automatically generate the "SEND" signal is described in U.S. Pat. Nos. 4,658,096, 4,737,975 and 4,775,997. According to these patents, an interface device detects the end of dialing and automatically appends a "SEND" signal to the dialed digits sent to the cellular telephone transceiver. However, in order to detect the end of dialing, such interface device requires additional circuitry to determine how many digits the dialed telephone has and then count the number of dialed digits actually received. Thus, adding a "SEND" button or circuitry that simulates the "SEND" function as in the prior art described above requires additional circuitry and increases the cost and complexity of the cellular telephone. For the foregoing reasons, there is a need for a cellular telephone which does not require generation of the "SEND" signal.